Conjugated diene polymer compositions stabilized with certain hydroxylamines



United States Patent M 3,432,578 CONJUGATED DIENE POLYMER COMPOSI- TIONS STABILIZED WITH CERTAIN HYDROXYLAMINES Jon W. Martin, Los Alamitos, 'Ca]if., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 5, 1964, Ser. No. 401,637 US. Cl. 260-880 7 Claims Int. Cl. C08d 11/04; C08f 45/60, 15/04 ABSTRACT OF THE DISCLOSURE Conjugated diene polymers are stabilized against the adverse eflects of ultraviolet light by adding a small amount of a hydroxylamine of the formula r R-NR wherein R is selected from aryl and aralkyl radicals.

This invention relates to the stabilization of conjugated diene polymer. More particularly, it is especially con cerned with the protection of certain block copolymers from the adverse effects of ultraviolet radiation.

The stabilization of polymeric materials has been investigated in many aspects. Broadly, stabilizing substances are utilized for One of several reasons; namely, to prevent oxidation by atomospheric oxygen or its equivalent, to minimize the effect of ozone, to depress the adverse effects of ultraviolet light or its equivalent and to minimize the effects of cross-linking or depolymerization and the attendent change in physical properties such as reduction in flexibility or increase in brittleness, another major concern is to discover classes of materials which will stabilize a given polymer in one or more of the above, respects, but at the same time will do so without unduly increasing the color of the stabilized composition. I

The influence of ultraviolet light upon polymers and particularly upon polymers prepared from conjugated diene monomers is of prime importance in many of the end uses for such products. These include, for example,

coatings, moldings, laminates, safety glass adhesives, film, fibers, and the like. If the polymer is sensitive to either cross-linking or degradation under the influence of ultraviolet light, the properties of the polymer change radically and the products made therefrom shortly become unsatisfactory in one physical property or another.

It is an object of the present invention to provide improved compositions stabilized against the influence of ultaviolet light. It is another object of the invention to pro vide elastomeric compositions having improved stability relative to ultraviolet light. It is a particular object of the invention to provide improved block copolymers of conjugated dienes stabilized against ultraviolet light. Other objects will become apparent during the following detailed description of the invention.

Now, in accordance with the present invention, conjugated diene polymers are stabilized against the effects of ultraviolet light to an unexpectedly great degree by the presence of a stabilizing minor portion of a diarylhydroxylamine. Still in accordance with the present invention, a particular class of such conjugated diene polymers is especially responsive to the influence of dibenzylhydroxylamines (including alkyl-substituted dibenzylhydroxylamines), said class comprising of those having the general structure:

wherein each A is polyvinylarene block and B is a poly- 3,432,578 Patented Mar. 11, 1969 diphcnylhydroxylamine dibenzylhydroxylamine phenylbenzylhydroxylamine dinaphthylhydroxylamine di phenylethyl hydroxylamine di (2,4-dimethylphenyl) hydroxylamine Of the above, dibenzylhydroxylamine and its alkyl derivatives wherein the alkyl groups are substituents on the aromatic ring are preferred for the present purpose. They may be used in relatively wide amounts (usually 02-25% by weight based on the polymer) dependent upon the conditions to which the composition will be subjected as well as upon the specific block copolymer being so stabilized.

The block copolymers may be either elastomeric or thermoplastic in character dependent not only upon the individual average molecular weights of the various blocks, but upon the ratio of a thermoplastic end block relative to the elastomeric center block. The ultraviolet sensitivity of the block copolymers usually increases directly with the portion of the conjugated diene center block.

Typical block copolymers especially contemplated have the general structure:

polystyrene-polyisoprene-polystyrene and polystyrene-polybutadiene-polystyrene The hydroxylamine may be mixed with the polymersunder any suitable conditions such as, by dissolving the hydroxylamine in a cement of the polymer in a suitable solvent after which the stabilized cement may be used as such for purposes such as, the formation of surface coatings, film or fiber extrusion, etc., or the composition may be coagulated such as by precipitation in hot water to form polymer crumbs. These in turn may be compounded with other polymer composition components including pigments, plasticizers, extenders, reinforcing agents, curatives, sulfur, and the like. Supplementary stabilizers may be used as well.

The subject diaryl (including arylalkyl) hydroxylamines not only provide protection against the deleterious effects of ultraviolet light but also appear to stabilize the polymer during hot mill mixing and unexpectedly provide internal lubrication for the composition.

The degradation of the subject block copolymers in the presence of sunlight is apparently accelerated in contact with oxygen. This degradation, however, is minimized by the presence of the subject hydroxylamines. The effectiveness of the diarylhydroxylamines is found to be dependent upon the type of substitution. Hence, the comparative data contained in the working example shows that dialkylhydroxylamines are completely ineffective for stabilization against the effects of ultraviolet light in the protection of block copolymers.

3 The following comparative data illustrate the advantages gained by the use of the preferred species of the diarylhydroxylamines for the stabilization of a block polymer having the general configuration:

The compositions of this invention, being outstanding in their stability with respect to sunlight or other source of ultraviolet, are particularly suitable for outdoor exposures such as in the form of fibres or films as well as 6 coatings, lacquers, and elastomeric protecting surfaces. polystyrene polybutadlene polystyrene They may be modified by the presence of other polymers Whefelh the average block molecular Weights are 12,000- such as polyolefines, polystyrene, or other elastomers. 44,00012,000. The base polymer was modified with the I claim as my invention; following compounding ingredients: Base P y is h 1. A conjugated diene polymer containing a stabilizing block eoPolYIher of Styrene M- 1 amount of a hydroxylamine selected from the group con- (44,ooo)'styrehe This was In l form sisting of: diphenylhydroxylamine, dibenzylhydroxyl- PP f extrudatel- These Were mlll'massod amine, phenylbenzylhydroxylamine, dinaphthylhydi'oxylthree minutes on a 6" laboratory mill at 150 C. roll amine, di(pheny1ethy1)hydroxylamine and 2 4 i h temperature. They were then pressed at 140 C. for ten ylphenynhydmxylamine, minutes to form Sheets of (llmehsioh X X 2. Polyisoprene containing a stabilizing amount of ahy- These Sheets Were used for the t e$t1hgdroxylamine selected from the group consisting of: dithe addition o the stebllllers, the h were phenylhydroxylamine, dibenzylhydroxylamine, henylmilled for the three minute period at 150 C. in the presbenzylhydroxylamine, dinaphthymydmXyhmine di(phenence of powdered or liquid stabilizers. Mixing was assisted ylethynhydmxylamine and 2 4 1 h 1 h by use of a doctor blade. The base polymer was further droxylamine' modified as indicated in Table I below with a number of p l di Polymer containing a stabilizing potential stabilizing additives after which the compositions amount of a hydroxylamine Selected f the group were exposed to ultraviolet light under standard condi- Sisting diphenylhydroxylamine, dibenzylhydl-oxylhohsamine, phenylbenzylhydroxylamine, dinaphthylhydroxyl- The above sheets were symmetrically placed on a 16" amine, di(phenylethyl)hydroxylamine and 2 4 i diameter turntable which rotated at 1 rpm. and was ylphenyl)hydroxylamine covered with white cardboard. Two GB 275 watt sun- 4' A block copolymer of Styrene and a conjugated lamp bulbs were located apart and ahove the diene containing a stabilizing amount of a hydroxylamine Samples- The ehflre System above was Placed m a selected from the grou consisting of: diphenylhydroxyl- 'fl y hlgh enclosed metal compartment having amine, dibenbylhydroxylamine, phenylbenzylhydroxylshver Pamted WahS- amine, dinaphthylhydroxylamine, di(phenylethyl)hydrox- The effect of ultraviolet light upon the polymers was ylamine and di(24 dimethy1pheny1)hydroxylamine tested by the change in melt fiow index which was ar- 5' A block copolymgr having the Structure f 1 bitrarily determined by measuring the rate of flow in grams styrene polyisopl-ene polystyrene containing a Stabilizing P 10 fhlhutes thmhgh a stahdardhnhce after h h amount of a hydroxylamine selected from the group confor a given length of time. According to the table it will sisting diphcnylhydroxylamine, dibanzylhydroxyp be seen, that the control sample and samples stabilized amine phenylbenzylhydroxylamine, dinaphthylhydl-oxyl with either the phenylsalicylate or the benzyltriazole as i di( henylethyl)hydroxylamine and di(2,4-dimethwell as with the diethyl hydroxylamine rapidly degraded ylphenyl)hydroxylamine even in the course of the first hour of exposure to ultra- 40 6 A block copolymer having the Structure polystyrene violet hghtcompared with this: however the modihca' polyisoprene-polystyrene containing a stabilizing amount tion of the base polymer with dibenzyl hydroxylamine of dibenzylhydmxylaminel provided a substantially greater stabilization against the Polyisoprene containing a Stabilizing amount f ideleterious effect of ultraviolet light. benzylhydroxylamine TABLE I.RELATIVE UV STABILITY Sample Melt fiow 1 after time of exposure, 111'.

References Cited UNITED STATES PATENTS 1 2 3 4 5 gfiiiilfiiiaiaaiisiaasy'iz 3 3112 :::2 6 (i -4 59g 212 212 :iijiiiiiiijiiijiiiiiij: 2M6 assatt-3555.3???- 0.. 0,. FOREIGN PATENTS C0ntrol+0.2 phr.dibenzyl- 584,203 9/1959 Canada. c$liil-f.li i.%$l?'aii5aa;yi GEORGEF LESMES hydroxylamine 4.0 3,8 3.7 2, wy Ex miner.

1 G. flow per 10 minutes.

2 All samples contained 1.5 phr. 2, 6-di-tert-butyl-4-methylphenol,1, 3, 5- trimethyl-2, 4, (rtris (3, 5-di-tert-butyl-4hydroxybenzyl) benzene and dilaurylthio dipropionate and 0.1 phr. liguin sulfonate.

US. Cl. X.R. 

